Well...a lot of what I know about the modern Japanese political scene comes from the book I linked in my other post alongside keeping up with the news from there. For a quick and dirty setup though...
The reason why Japan has effectively been a one-party state since the end of the war largely stems from one man - Kakue Tanaka. Originally a nobody from a poor family in what was then the most backwater area in all Japan, he eventually became involved in construction before going to Tokyo to strike it rich. While there, he began a drafting firm before being drafted into the IJA. After a short stint in the army, he went back to Tokyo and took over a construction company and became heavily involved in government contracts; building heavy industry in Korea, Manchuria, etc. (as an aside, it's rumored his company was involved in the
Japanese nuclear weapons project F-Go) Anyhow, before the war ended he could tell Japan would lose...and subsequently cashed in all his war bonds to a nice sum of money ontop of the governmental contract funding he'd gotten.
Back in his hometown, he decided to run for office - which at first he lost, before winning in '47. The same year he'd switch parties from the Democratic Party to the Democratic Liberal Party.
The next year would be his promotion to minister of justice, where he'd further his connections and be arrested for bribery - which he denied, and continued his political career even though his party distanced itself from him. He was found guilty of bribery three years later, but he appealed (and this appeal would go on for a while). He famously said, "A man must never be afraid of going to jail The 50's would also be when he discovered how pork barrel politics could be helpful; he bought and refurbished a poor railway in his district, to which he had well over the needed votes to be reelected.
Oh, he was also once promoted to being the head of the ministry for international trade and industry, which allowed him to spread his grand idea of a remodeled Japan throughout the government. During this time he also gained a reputation for not following the whims of the Americans and negotiating down tariffs, while also gaining friends in the US press and industry.
From hereon, he'd be affiliated with the LDP as well after the DLP was absorbed by it. Under the LDP, he became the minister of telecommunications - which he used to his benefit, alongside recognizing how media can be used to shape popular opinion. I remember reading something about he'd give licenses to near anyone who applied, unlike previous ministers.
Eventually he'd command a sizable portion of the main LDP faction which he used to form the basis of his own faction; the gundan. What made his faction so powerful was he supported everyone, regardless of whether they'd win or not - if politician x from town y needed a campaign team, money, and training they'd have it all and more. Mistresses were found for those who wished, paid off, etc. In return all they'd have to do was to keep supporting him.
Using his powerhouse base, he became prime minister in '72. He began all kinds of public works in both Niigata and whereever else in order to fulfill his dream of a modernized and wholly new Japan. However, alongside this, he also used shell companies connected to him to buy up land before then purchasing it for public works...in other words, gaming the system. It was discovered by the Japanese press, but the public didn't mind so long as the good times kept rolling. Eventually the Watergate Scandal brought him down from being the PM of Japan. During one of his nightly calls, Tanaka had agreed to take a payment of $2mil from Lockheed to outfit JAL. He was caught, but the case was dragged out in court through his connections (it only met once a week on Thursday) and when convicted, he appealed and thus avoided jailtime...and allowed him to keep a hand on things. He would die in 1993
His group kept itself intact for the most part, although it had a subfaction within itself which was headed by two guys who were pretty trusted by Tanaka - albeit this relationship would falter when one of them was taken down by two scandals - one I can't remember and the
Recruit scandal. Uhh...from there the group eventually splintered, with a new political party being formed, more infighting, more corruption, the bubble popping, Tanaka's hand still vaguely guiding Japan through the LDP's policy of big government spending, and many of his former "students" winning the prime ministership.
Like Koizumi, or
Nakasone
It's uh....a lot. Definitely suggest the book.
As another aside to all this...part of the reason why Japan hasn't recovered from the recession in the 80's is due to the massive public spending; they can't increase it any more than it is, and if they decrease it then it just gets worse. On the "plus" side though as long as the LDP gets your vote, you'll get nice kickbacks.
